as you stated causal has the problem of income and indie has the problem of exposure.
then in theory if you bind these 2 together you got a huge pile of sht off your head.
next question: is it possible?
yes it is.
the stuff that scares me, that i played a vast variety of causal games and did not saw your site till today. how the hell do you still manage to sell a game?
what i think works for best to get a causal out on the portals what is exactly or at least resembles the real deal you sell on your site. be careful, if you screw up the causal game, you might have to rename your site. and do not - in any case - name your causal version "demo". you might get some payment from advert to. i mean if you get it right a sht game can get you more then the next big thing.
on the other hand the causal business is pretty open for newcomers and there are a ton of references out there. especially case studies. they are my favorite, they tend to go directly for business.
and people will certainly pay 50 for a good multiplayer. advertise multiplayer a bit more. and make a game based on that.